Postpolio Syndrome

Gale Encyclopedia of Medicine, 3rd ed.
COPYRIGHT 2006 Thomson Gale

Postpolio Syndrome

Definition

Postpolio syndrome (PPS) is a condition that strikes survivors of the disease polio. PPS occurs about 20-30 years after the original bout with polio, and causes slow but progressive weakening of muscles.

Description

Polio is a disease caused by the poliovirus. It most commonly infects younger children, although it can also infect older children and adults. About 90% of people infected by poliovirus develop only a mild case or no illness at all. However, infected people can continue to spread the virus to others. In its most severe form polio causes paralysis of the muscles of the legs, arms, and respiratory system.

About 1% of all people infected with poliovirus develop the actual disease known as polio. In these cases, the virus (which enters the person's body through the mouth) multiplies rapidly within the intestine. The viruses then invade the nearby lymphatic system. Eventually, poliovirus enters the bloodstream, which allows it to gain access to the central nervous system or CNS (the brain and spinal cord). The virus may actually infect a nerve elsewhere in the body, and then spread along that nerve to enter the brain.

The major illness associated with poliovirus often follows a mild illness, which has symptoms of fever, nausea, and vomiting. However, after a symptom-free interval of several days, the patient who is on the way to a major illness develops new symptoms such as headache and back and neck pain. These symptoms are due to invasion of the nervous system. The motor nerves (those nerves responsible for movement of the muscles) become inflamed, injured, and destroyed. The muscles, therefore, no longer receive any messages from the brain or spinal cord. The muscles become weak, floppy, and then totally paralyzed (unable to move). All muscle tone is lost in the affected limb, and the muscle begins to decrease in size (atrophy). The affected muscles are often only on one side (asymmetric paralysis) of the body. Sensation (the person's ability to feel) is not affected in these paralyzed limbs.

The maximum state of paralysis is usually reached within just a few days. The remaining, unaffected nerves then begin the process of attempting to grow branches to compensate (make up for) the destroyed nerves. This process continues for about six months. Whatever function has not been regained in this amount of time will usually be permanently lost.

Causes and symptoms

PPS occurs in about 25% of patients, several decades after their original infection with polio. However, long-term follow-up indicates that two thirds of polio survivors may experience new weakness. Several theories exist as to the cause of this syndrome.

One such theory has looked at the way function is regained by polio survivors. Three mechanisms seem to be at work:

injured nerves recuperate and begin functioning again

muscles that still have working nerve connections grow in size and strength, in order to take over for other paralyzed muscles

working nerves begin to send small branches out to muscles whose original nerves were destroyed by polio

As a person ages, injured nerves that were able to regain function may fail again, as may muscles that have been over-worked for years in order to compensate for other paralyzed muscles. Even the uninjured nerves that provided new nerve twigs to the muscles may begin to falter after years of relative over-activity. This theory, then, suggests that the body's ability to compensate for destroyed nerves may eventually begin to fail. The compensating nerves and muscles grow older, and because they've been working so much harder over the years, they wear out relatively sooner than would be expected of normal nerves and muscles. Some researchers look at this situation as a form of premature aging, brought on by overuse.

Other researchers note that normal aging includes the loss of a fair number of motor nerves. When a patient has already lost motor nerves through polio, normal loss of motor nerves through aging may cause the number of remaining working nerves to drop low enough to cause symptoms of weakness.

Other theories of PPS include the possibility that particles of the original polioviruses remain in the body. These particles may exert a negative effect, decades later, or they may cause the body's immune system to produce substances originally intended to fight the invading virus, but which may accidentally set off a variety of reactions within the body that actually serve to interfere with the normal functioning of the nerves and muscles.

Still other researchers are looking at the possibility that polio patients have important spinal cord changes which, over time, affect the nerves responsible for movement.

Survivors of polio may also develop arthritis of the spine, shoulders, or arms, related to the long-term use of crutches or overcompensation for weak leg muscles.

Diagnosis

Diagnosis is primarily through history. When a patient who has recovered from polio some decades previously begins to experience muscle weakness, PPS must be strongly suspected.

Treatment

Just as there are no treatments available to reverse the original damage of polio, there are also no treatments available to reverse the damaging effects of post polio syndrome. Attempts can be made to relieve some of the symptoms, however.

Pain and inflammation of the muscles and joints can be treated with anti-inflammatory medications, application of hot packs, stretching exercises, and physical therapy. Exercises to maintain/increase flexibility are particularly important. However, an exercise regimen must be carefully designed, so as not to strain already fatigued muscles and nerves.

Some patients will require new types of braces to provide support for weakening muscles. Others will need to use wheelchairs or motorized scooters to maintain mobility.

Sleep problems and respiratory difficulties may be related to each other. If breathing is labored during sleep, the blood's oxygen content may drop low enough to interfere with the quality of sleep. This may require oxygen supplementation, or even the use of a machine to aid in breathing.

Prognosis

Prognosis for patients with post polio syndrome is relatively good. It is a very slow, gradually progressing syndrome. Only about 20% of all patients with PPS will need to rely on new aids for mobility or breathing. It appears that the PPS symptoms reach their most severe about 30-34 years after original diagnosis of polio.

Prevention

There is no way to prevent PPS. However, paying attention to what types of exertion worsen symptoms may slow the progression of the syndrome.

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Post-polio Syndrome

Post-polio syndrome

Definition

Post-polio syndrome is a slowly progressing weakness that affects polio survivors decades after their initial bout with the disease.

Description

In order to understand post-polio syndrome, it's important to understand polio infection in general. Although people of any age can become infected with poliovirus, it tends to infect young children in particular. About 1% of all people who become infected with poliovirus will actually become ill. Initial symptoms include fever, nausea,

and vomiting, followed by several symptom-free days. Some individuals then recover completely. Others go on to develop new symptoms, including severe head, back, and neck pain . These symptoms signal that the virus is invading the nervous system, causing inflammation, injury, and destruction of motor nerves (the nerves that are necessary for muscle movement). As motor nerves are destroyed, the muscles cannot receive messages from the brain. Without input from the brain, muscle tone becomes weak and floppy, and paralysis sets in. Over time, the muscle becomes atrophic (shrunken in size). Paralysis is usually asymmetric; that is, it affects only one side of the body. The paralyzed limbs retain their ability to feel. When the muscles of respiration are affected, the patient may need to be put on a mechanical ventilator.

It only takes a few days for the weakness and/or paralysis to progress to its maximum level of severity. Recovery continues for about six months, during which time the remaining unaffected motor nerves begin sprouting new branches to the muscles, in an attempt to compensate for the nerves that were completely destroyed. During this phase, the patient will regain some degree of functioning. After six months have passed, whatever disability remains will usually be permanent.

Post-polio syndrome occurs some decades after the original infection with polio. Initially, the subtly gradual progressive muscle weakness is barely noticed by the patient, but over time the decrement becomes increasingly obvious. In general, the more severe the original polio infection, the more severe the disability from post-polio syndrome.

Demographics

Only 1% of all people infected with poliovirus actually develop full-fledged polio. About 25-50% of polio survivors will eventually be affected with post-polio syndrome.

Causes and symptoms

Attempts to completely delineate the process by which post-polio syndrome develops have not been totally successful. A number of working theories have been developed.

The newer nerve sprouts that grew in order to compensate for lost motor units overtax the rest of the nerve, and over time the nerve begins to fail.

Injured nerves that regained function end up failing after years of overuse attempting to compensate for lost motor units.

Remaining particles of the poliovirus may precipitate a chemical response in the immune system that accidentally destroys the body's own nerves.

Symptoms of post-polio syndrome include severe fatigue ; decreased energy; gradually progressive muscle weakness and muscle atrophy; involuntary muscle twitching (fasciculation); muscle, joint and back pain ; difficulty breathing and swallowing; and problems with sleep. The most severe muscle problems seem to occur in those muscles that were already affected by the initial bout of polio, although muscles that were not originally affected may also develop some new degree of weakness.

Diagnosis

Diagnosis should be suspected in any polio survivor experiencing new muscle weakness.

Four criteria are required to diagnose post-polio syndrome in a patient with gradually increasing muscle weakness:

known history of poliovirus infection with residual muscle weakness

history of recovery of some degree of muscle function, with a period of stability lasting at least 15 years

normal function of sphincter muscles (the muscles around the anus and the lower part of the esophagus)

Treatment team

The treatment team will depend in part on the specific symptoms encountered. In general, once diagnosed, the patient will benefit from work with a physical therapist, occupational therapist, and speech and language therapist. Specialists in arthritis, orthopedics, rehabilitation, and pulmonology may also be helpful.

Treatment

There is no cure for post-polio syndrome. Efforts are primarily directed at retaining mobility and improving patient comfort. Anti-inflammatory medications can help relieve muscle and joint pain by decreasing inflammation. Braces, wheelchairs, or motorized scooters may help very compromised patients retain some independence and mobility. Respiratory and sleep problems may interact with each other to create considerable distress. They may be relieved by the use of supplemental oxygen and/or breathing devices to help keep the airway open while sleeping.

Recovery and rehabilitation

The physical therapist should design a thoughtful exercise program to maintain and increase flexibility, although it is important not to overtax already weakened muscles and nerves. Occupational therapy can help the individual learn methods to compensate for muscle weakness, and still retain independence in the activities of daily living. Speech and language therapists can be helpful for swallowing problems.

Clinical trials

A clinical trial through the National Institute of Neurological Disorders and Stroke is studying whether the drug modafinil might be helpful in treating the relentless fatigue of post-polio syndrome.

Prognosis

Because the increase in muscle weakness is so gradual, post-polio syndrome is generally thought to have a good prognosis, rarely causing significantly more severe impairment and disability. In a few rare cases, however, progressive weakening of the muscles of respiration can result in death.

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post-polio syndrome

post-polio syndrome (pohst-poh-li-oh) n. insidious numbness in muscles, together with fatigue and pain, that develops 15–20 years after an attack of poliomyelitis. It may be caused by loss of nerve cells that have been under greater strain than normal; there is no evidence of reactivation of the poliovirus.

Cite this article Pick a style below, and copy the text for your bibliography.

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